Sound-detecting device



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RICE. GEF SGHENECTLDY, NEW' YRK, ASSIGIXOB T() GEJEEAL ELETREC CMPMY, .Il CORPGRATION 0F NEW YGRX.

soennnnrno'rme envien.

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pplcation ile fune 5"" invention relaties to devices for de- ,'5 sounds or similar vibrations transd through :t [luid medium and is espe- .ily useful, 'for detecting,r the sounds enianating 'from various sources such es sub 'i l stations,submarine and other ooiver prop. d bontslor the like.

In carrying out my invention in practicea l may utilize a inicrol'ihonc, 'for exemple one oi the inertia type, so arranged to receive the vibrations 'from the l'luid medium through an interposed body ot a material such as soft rubber having non resonant apefidic character-istics.v This body ot' soit4 rubber is in the form ot n diaphragm-whicii supports or carries the microphone and preferablyv in an unstrained and unstretchcd condition. Yl`he sounds thereby collected by the microphone i: ,fd rendered apparent to an observer by the use, in the ordinary Way, of an electric telephone receiver, reach the observerjfree from distortion eli'ects due to resonance, and unaccompanied by extraneous sounds of any kind produced in the apparatus itself. The sound'thus rendered apparent is a faithful reproduction corresponding to the sound waves coming; thro L the liquid or subaqueous medium to 'the device. The microphone is supported upon soft rubber di phragm to avoid the resonance eliects which might occur it the n'iicrophones were supported on metal, Wood or similar resonant material which would magnify certain sound vibrations and tend to produce n false qualiti'v in the sound perceived in the telephone receiver. For the purposes for which devices of this hind are commonly used a false reproduction or en alteration in quality ot' the sound received by the microphones is a' serious fault.

yIhe scope of my invention will be particularly pointed ont in the appended claims, While the invention itself will be better understood by reference to the following description and the nccoriipeying drawings,

in which l. is a Viewv in perspective of a device embodying my invention. While Fig. 2 is an enlarged sectional View of the same.

'The sound receiving device made in accordance with my invention, though not necessarily limited to use under Water is nevertheless adapted for that. purpose, and

to this end it is constructed so that itsin- 'pert'i'irzitions in 'the dislirom side to Side and. thus firmly secures or eres it in place. y The microphone element is supported on the shank 3, which centrally drilled and tapped to hold it. rlhis microphone elenient, shown partly in section in lligz. 2, and. in the main ot usual construction, comprises a brass easing or cup 4 containing carbon grannle; 5 in contact with one carbon plate or terminal (l 'resting on the bottoni of the cup and also with a second carbon plate or terminal-7, electroplated on one side, and soldered on that side to a disk 8 of brass provided with athreaded projection 9. The carbon terminals are separated trom the sides-of the cup by a ring of lelt l0, and the cup is closed by a perforated :nicadiaphragm 11 cemped between the disk 8 and a disk l). of l ass or other suitable materiel threaded on the `projection l) ot' the brass dish 8, and screwed downagainst the mic diaphragm. The brass casing: er cup 4 has a threaded supporting stud 13 integralwith or riveted to it to screiv into the shank 3 conducting material, fastened to a metal ring,r spun about the flaring lip of the cup l' and in electrical contact through the cup with the carbon terminal 6. A flexible terminal Wire l5 leading to the microphone is mechanically and electrically connected t0 the bail 14 while the other flexible terminal Wire 15 is xnechanically connected to but insulated from the bail by an insulated terminal 17, which is connected througi'i e Very flexible wire 18 to the threaded projection 9 and thence to the 'carbon plate or tei-mmol 7. To enclose the microphone 1n e, Water tight external circumferential grooves and, iittedv tightly into the rubber cup 1. This thimble is counterbored at the outer end to receive various members which cooperate to produce a water tight closure, while the open inner end of the thimble leaves the bottom, of cup free to act as a diaphragm. A brass disk 20 fitting snugly in the counterbore of the thimble 19 has on .its edge a groove for holding a drying agent, preferably metallic calcium in the form o' a number of turns of wire 21. The slow diffusion of the air contained in the interior of the thimble and cup 1 through openings 22 into the groove 21 .and over the calcium wire keeps the air perfectly dry.

Electrical Aconnections with the microhone are made through the terminal Wires 15 and 16 by leadin T-in wires 23 and 2li1 heavily coated'with rubber 25 and 26 and fitting tightly into holes in the brass disk 2O and also linto holes in a solid block 27 of softrubber which presses against the grooved brass disk 20. y To compress the rubber 27 firmly about the wires and against the disk I provide a follower disk 28, preferably of brass, and having holesl tor the wires. er disk is driven against the rubber block 27, expanding it outwardly against the thimble 19 and inwardly against the leading-in wires to form an absolutely water-tight joint, by means ot a follower ring 29 screw threaded into the outer end of the thimble 19. A lock washer 30 of phosphor bronze or similar spring metal between the follower disk and the ring keeps the parts under constant compression in case they should have a tendency to give through the action of time or other influences.

In many cases it is advisable to clamp the rubbervcup 1 to the thimble 19 by a clamp 31, locked' by a screw fastener 32 in place around the cup so as strongly to. compress it against the thimble.

By constructing the vibrating diaphragm as the base of a cup-shaped member and holding the diaphragm in place by clamping the side wall of the cup against the side wall of the tubular support 19, leakage past the edge ot the diaphragm is prevented without squeezing ot' the edges of the diaphragm. Squeezing of the edges of the diaphragm would force the material thereof toward the center of the diaphragm and produce a loose, liabby construction which would interfere with proper sound transmission. Moreover. the location of the clamp away from the diaphragm permits a tree adjustment of the edges of the diaphragm when the diaphragm is pressed into the tube by heavy water pressure.

The follow-L Malacca 4'oitV the thimble 19. A reentrant portion 34' ot this cover tits into .the interior of the follower ring 29. v

Vlhen the device above described is immersed in a sound conductingl liquid medium the sound waves act upon the bottom of the cup 1, which forms a rubber diaphragm for supporting the microphone, and cause vibrations to be transmitted te the carbon granules and carbon terminalsl by reason of the inertia of the parts of the microphone. As already explained, the variations in resistance of the .microphonel circuit due to these sound vibrations maybe disturbed, in y case the device is used in the open sea, by variations in the hydrostatic.headbfwater above the device due to the rise and, fall of the waves. The pressures due tg. water waves are applied and released very slowly,

as ctmaparedr with the rapid varying pressures produced by a sound wave, and cause a slow oscillation of the diaphragm, so that the microphone is lmoved. bodily back'and forth. Any effect upon the micropho e of this slow movement or" the rubber diaph agm is prevented by` eliminating any factor which` would make the microphone button sensitive to slowly applied pressure. To this end the terminal Wires 14 and 15 leading ,to the microphone from the leads 23 and 24 are very lexible and are fastened mechanically to the bail 'l2 so that as the microphone is moved back and forth by the slow oscillation of the diaphragm these wires cause no variation in the pressure on the carbon granules of the L microphone,

Changes in air chamber produced f;

rubber bottom o'i pressure on the carbon granules pressure in the closed the cup 1 also vary the by the oscillations of the ii the casing 54 of the microphone 1s tight. To preventI l these pressure variations thebrass casing 4; may be ventilated by perforations 35 which equalize the pressure in the closed chamber and in the casing 6. l

I do not lay claim to the ventilated construction for the microphone as heretofore described nor to the use'of the bail 14, as these features are described and claimed in companion applications of Albert W. Hull Serial No. 302.232 and Irving Langmuir Serial No. 302,279.

Sound detecting devices such as herein described may be used singly if desired, but are especially' useful in pairs or in triplets, for determining the direction sound comes by means of the binaural sense possessed by the human ears. @When Isound is transmitted to the hun'ianears from a point which is not equally distant4 from the from which ativo ears of the observer, the sound` arrives at one eer later than at the other because of the different distances which the sound has to travel to reach the tivo ears. The seme sound impulses ere'therefore not received simultaneously et the two ears of the observer und in sonic wey due to this eiiect the brein receives the impressionthet the source. ci scund is either st thecne side or the other. the observer. This 'eiiect is less pronounced the purer the quality of the sound received. :in the case, for exemp e, of e pure tone, such as that of s tuning` fork, or a telephone receiver fed with sine Wave alternating current, the binaurul sense can only with creat, diiiiculty determine the direction OI the sound. lvl/1ere, however, the sound includes sharp peaks other salient and recognizable variations or characteristics the binsural eiiect is much .more ecute. The use 'ot' :i soft rubber disphrsgm to support the micro phone es heretofore described is of especial velue Where devices of this general charater are to be used hinein-elly, as-,it avoids any resonance effects such as might occur if diaphragme metal, wood or the like were employed, which resonance yciiccts `would, by magnifying sound vibrations forming' no essentiel portion ot the sounds to be listened to, have a tendency to produce s false quality in thc sound perceived through the inicrophone. As the binnurul sense seems to depen-'l upon some kind o ccmperison of some salient cluuacteristics ot the sound to be listened to,this sense is interfered with seriously Where a false rcproduction of the received sounds is produced by resonunt eil'ects produced in the receiving apparatus itself.-

lilfhile I have shown u microphone of the urbon grunule type it is evident that n'iicrorphones of other varieties muy be employed us Well us devices or any other character such magneto-pliones or the like which will lieve the cfi'c y of producing variations in en electric current. in rc'iionsc to the vibrations ci the rubber vibrutory diuphrugm herein shown. lWhile other muteriul havin;r the desired characteristics oi soi't rubber muy be employed in pince thereof, .sott rubber `@gives the best results for the purposes in hund of any material with which l um acquainted.

'It to be observed that in the device which l here disclosed the rubber dinphrugin supporting' or carrying the microphone is in im misti-tuned und unstrctched condition und I consider this :i valuable quality. The fact that rubber is of approxiinutclv the same density as u'utcigin which it is.v immersed, contributes to the nonresonent quality ot` the diaphragm under the conditions of use.

The diaphragm upon which the -microphono is mounted should be vvery thick to securethc best results. As .shown inv Fig. 2, the thickness of'this diaphragm is about three-fourths oi the clear distance between its opposite points of support. it bus been found in practice that such s diaphragm is less resonant, that is, it .has a less pronounced naturel period of vibration, than e thin diaphragm in Which 'lt-he thickness.

might be one-fifth ot' the distance between the opposite points of supports, or l ss. rFhis more perfect aperiodic qualit," of the thick diaphragm is believed to be d1 e to the large volume of material throughout which the energy of vibration is dissipated, and to the fact that the thick diaphragm acts as a beam in resisting the water pressure and in rehund. the heavy water pressure is ordinarily insuilicicnt to crowd the whole bulk ot' the diaphragm into the supporting tube. The Water pressure is resisted by the sheurirmy stresses and compressive stresses which'urc engendered in the diaphragm after the manner in which stresses are engendered in a beam. But, whatever the eirplanation muy be, it has been very clearly establishedthatthe thick diaphragm such es shown in Fig. 2, which was regularly used for the detection of submarines duringl the wer, was less resonant, more aperiodic, sind generally nun-c cli'icicnt thun thin diuphrugms. The advantages ofthe 'thick diaphragm became very apparent at depths of fifteen feet and upward.

. lVhnt I claim es' new und desire to secure by Letters lutcnt of the United btutcs` is: y

l. The combination of a body of rubber having a recess therein with one wall pro porti/mcd to transmit sound vibrations, means for closingy said recess against the access of Water, electrical conductors comn'iunicutinur Withfseid recess -(ind e microphone mounted on said .wall ofgsaid rubber body to respond to sound vibrations trans` mittcd through scid rubber wall.

2. A sound detecting device comprising a Wull of soft rubber completely enclosing' u.

space, a portion of the enclosing soft rubber ivull being' adapted to vibrate in responseto sound vibrations, e. current varying device mounted on seid vibratory portion of the `great as the distance enclosing Wall, and conductors o'electric current connected to said current varying device. y

'3. The combination lot a rigid tubular member open at both ends, eoitt rubber cups In combination, Water tight casing, a

thick diaphragm forming a portion ot' the wall of' said casing, said diaphragm being composed of material which has substantially the damping characteristics of softrubber, `a device supported upon saidV dia'- phragm 'for causing variations in an electrical. current corresponding to vibrations of said diaphragm, and electrical conductors leading to and connected Hwith said current varying device. I

5. In combination, a watertight casing, a soft rubber diaphragm forming a portion oi' the wall ot said casing, the thickness of saiddiaphrag'm being more than one fifth of its diameter, and said diaphragm having a' substantial portion thereof under compression When vsubmerged to considerable depths, a microphone supported upon said diaphragm, and electrical conductors leading to and connected with said microphone.

t5. In combination, a. water tight casing, a diaphragm forming a portion ot the wall thereof, said diaphragm formed of a niaterial which has substantially the same vibratory qualities as sott rubber, means for supporting said diaphragm with a portion thereof free for vibration, the diaphragm being more than one-fifth as between its opposite points-ot support, a microphone in said casing mounted on said diaphragm, electrical conductors cxtendinginto said casing and connected to said microphone.

7. A vibration detector comprising a diaphragm oi soft rubber and means for Supporting the same for vibration in response '.:o sound vibrations, a current varying" device supported upon said diaphragm, the

thickness of said diaphragmv being approxl- A mately as great as threefourths ofthe diameter of its vibrating portion.

8. A vibration detector comprising a casing having an aperture therein, a rubber the thickness of ring to support the current-varying diaphragm closing and sealing such aperture, a bushing member embedded in the diaphragm, a current-varying device, and means forl attaching the current-varying device to the bushing member so that the current-varying device is supported within thc casing upon the rubber diaphragm.

D. A vibration detector for use under water, comprising a water :tree chamber, a rigid tubular member, and a cup composed of a material which has substantially the same vibratory qualities as soft rubber, the cup being mounted upon an open end of the tubular member so that the bottom of the4 cup tonstitutes a portion of the Wall of the Water. 'free chamber, and the side Wall of thel cup closely engaging the side Wall ofthe tubular member to hold the cup in place.

10. lA' vibration detector for use under water, comprising a Water free chamber, a rigid tubular member, and a thick-Walled cup composed of a material which has substantially the same vibratory qualities as sott rubber, the cup being mounted upon an open end ot the tubular member so that the bot-tom ot' the cup constitutes a portion of the wall of the Water Jfree chamber, and a clamp binding the side Wall of the cup upon the side Wall ot' the tubular member to hold 'the cup in place.

upon the side wall of the tubular member to hold the cup m place, a current-varying device mounted upon the bottom of the cup, and electrical conductors connecting with said current-varying device.

l2, Avibration detector comprising a cas- `ing'having an aperture therein, a rubber diaphragm closing and sealing such aperture, a bushing member embedded 1n the diing a threaded member engaging the bush- Y l device Within the casino. f

In Witness whereof, I have hereunto set my hand this 5th day of June, 1919.

CHESTER W. RICE.

aphragm, andla current-varying device hav- 

